PAHs, also known as polyaromatic hydrocarbons, which are composed of fused aromatic rings that do not contain heteroatoms, are an important class of compounds.
PAHs can be found naturally in oil, coal, and tar. They are produced as byproducts in combustion processes of fuel, be it fossil fuel or biomass. Being lipophilic, meaning they mix more easily with oil than water, PAHs dispersed into the environment are primarily deposited in soil, sediment, and oily substances, as particulate matter suspended in air, and in water. As a pollutant, they are of concern because some of the smaller (partially water-soluble) PAHs, such as benzo[a]pyrene, have been identified as carcinogenic, mutagenic, and teratogenic, and they are widely believed to make a substantial contribution to the overall burden of cancer in humans. A major route of exposure to PAHs for people is consumption of food, which can be contaminated from environmental sources as well as industrial or home food processing.
Considering the potential health risks associated with the release of PAHs into the environment, it is of fundamental importance to be able to detect and sequester these harmful molecules. To date, cyclodextrins (CDs) have been used most often to isolate PAHs from crude mixtures, although more recently derivatives of calix[n]arenes, cholic acid, and metalligand diazapyrenium-based metallocycles have been explored as potential suitors for PAHs of different shapes and sizes. It should be noted, however, that the metallocycles described by Quintela et al. incorporate heavy Pd and Pt ligand-metal coordination in order to form supramolecular architectures, which are expensive and would not be ideal from environmental and economical perspectives.